The objective of this proposal is develop an integrated, implantable, microtelemetric glucose sensor. This device is based on the glucose-sensitive swelling and shrinking of hydrogels that are confined within micromachined microcavities, but are in communication with body fluids through a rigid, porous, size-selective membrane. Swelling and shrinking forces are developed as a direct consequence of glucose complexation with pendant phenylboronic acid groups on the hydrogel, without mediation by enzymes such as glucose oxidase or hexokinase. This device does not require implanted batteries of transcutaneous wires. Swelling or shrinking forces, generated in response to changes in glucose concentration, impinge on a plate of a microcapacitor, altering its gap size and capacitance, leading to a change in the electromagnetic resonant frequency of a hermetically sealed, microfabricated circuit, which can be remotely sensed by a handheld or wristwatch-sized interrogating unit. In the present proposal we will investigate the effects of hydrogel composition, and material and geometric properties of the device components, on performance of the microsensorWe will then construct a prototype device for in vitro and in vivo testing. In vitro experiments will probe the devices[unreadable] ability to respond properly to changes in glucose concentration, and assess the effect of other chemical species, such as small saccharides and plasma proteins. In vivo experiments, performed in rats, will focus on the ability of implantable sensors to faithfully monitor series of step changes in blood glucose concentration.